The construction industry often requires that excavations be made in the earth. In many instances, it is desirable to support the earthen upright walls of the excavation in order to prevent collapse. A collapsed wall or walls would require re-excavation, thus, causing delay and increased costs. Moreover, a collapsed wall could cause injury or death to a worker situated in the excavation. Recognizing potential hazards to excavation workers, governmental agencies have enacted regulations which require shoring assemblies to support the upright walls of the excavation in order to protect the workers. One such shoring assembly is a protective structure commonly referred in the construction industry as a "trench box" or a "trench shield."
The trench box is disposed in a trench and is operative to buttress its opposing upright walls. The trench box has a pair of side panels which are operative to support each other in a selected spaced-apart relationship by a plurality of spreader beams. When disposed in the trench, the trench box shores or otherwise prevents collapse of the upright walls of the excavation. One example of a trench box is disclosed in my patent number 5,310,290. Other examples of trench boxes are found in U.S. Pat. No. 4,090,365 issued May 23, 1978 to Nieber and U.S. Pat. No. 4,202,649 issued May 13, 1980 to Cook et al.
Presently, there are two types of trench boxes being used in the construction industry. One type of trench box includes a pair of side panels with each side panel having a knife-shaped bottom edge. Each knife-shaped bottom edge is integrally formed as part of the side panel. This type of trench box which is commonly used in the construction industry is hereinafter referred to as a "knife-edged trench box." Another type of trench box which is less commonly employed in the construction industry has a flat bottom edge. This type of trench box is hereinafter referred to as a "flat-bottom trench box." Knife-edged trench boxes have advantages over flat-bottom trench boxes. First, under certain soil conditions, such as muddy soil or sandy soil, the flat bottom trench boxes are inadequate because the muddy or sandy soil seeps under the flat bottom edges and infiltrates the work space. To resolve this problem, knife-edged trench boxes are employed. A downwardly force applied to the knife-edged trench box positioned in the excavation embeds the knife-edged trench box into the floor of the excavation. The embedded portion of the trench box now prevents muddy or sandy soil from seeping under the side panels and into the work space. Second, as the trench is dug deeper within the work space between the side panels of the trench box, the knife-edged trench box can be advanced downwardly to cut along the upright walls of the excavation, thus aiding in excavation.
Although knife-edged trench boxes provide the contractor with advantages, there is a corresponding problem associated with stacking of the knife-edged trench boxes. Sometimes, it is desirable to stack the trench boxes on top of each other as the excavation is dug deeper in order to maintain compliance with governmental regulations. Since the knife-edges are integrally formed with the side panels of the trench box, only one knife-edge trench box can safely be stacked onto another by inverting the top one and stacking it on the embedded knife-edged one. Thus, knife-edged trench boxes can only be stacked two high. In some excavating applications, it might be required that three or four trench boxes must be stacked onto one another. Therefore, if the bottom trench box is to be embedded, both flat-bottom trench boxes and knife-edged trench boxes must be employed in order to safely stack more than two trench boxes.
To facilitate stacking more than two trench boxes, a selected number of flat-bottom trench boxes and knife-edged trench boxes must be delivered to the excavation site. Occasionally, additional trench boxes could be utilized to advance progress of the excavation. Sometimes, knife-edged trench boxes are needed and while other times flat-bottom trench boxes are needed. Presently, the only way to resolve this dilemma is to supply additional trench boxes of both types than is initially anticipated to be needed. However, this solution is not cost efficient.
Also, some trench boxes are three-sided while others are four-sided. In certain circumstances, it may be desirable to have all three or all four sides of the trench box to have knife edges so it could be embedded into the floor of the excavation. For other applications, it might be desirable to have knife edges used on only the side panels while the front and rear panels have flat bottom edges.
Another type of shoring assembly is a protective panel which is a single panel supported by a brace in order to buttress a single upright wall of an excavation. Again, depending upon soil conditions, it may be desirable to employ a protective panel having either a flat bottom edge or a knife edge. Presently, the contractor must select which type and how many of each are needed before the protective panels are delivered to the excavation site.
There is a need in the construction industry to provide a shoring assembly that includes a removable knife-edge structure. The present invention addresses this need.